Air-hardening steel alloy



LIM F. FINKL, OF CHICAGO, ILLINOIS, ASSIGNOR 'IO A. FINKL @L SONS COMPANY,

OF CHICAGO, ILLINOIS, A CORPORATION F ILLINOIS.

AIR-HARDENING STEEL ALLOY.

Continuation of application-Serial No.

of Illinois,have invented an Improvement in Air-Hardening Steel Alloys, of which the following is a specification. y

This invention relates to steel alloys which are particularly adapted for use in machine parts requiring great hardness, durability and strength, and has for its principal ob ject to provide an alloy of the class described capable of being air-hardened during heat` treatment, with a .iinimum danger of ,15 shrinking, cracking or warping of the piece.

In carrying out my invention, I utilize as afiloymg metals, chromium, molybdenum. In a copending application for United States Letters Patent, bearing Serial No. 467,201, filed May 5, 1921, of

which this application is a continuation, I have described a form of air-hardening chrome-nickel-molybdenum alloy which is particularly adapted for use in die-blocks,

' altho not restricted to such use. This alloy broadly includes' a steel alloy having the elements substantially within the following ranges:

Carbon .30 to 1.10% Nickel .50to 2.001% Chromium .25 to 1.10% Molybdenum .15 to2.00%

Other elements, such as manganese in fractions up to 1.00%, or silicon, in small fractions, may be present as is often the case in steels used in special alloys of this class.

My improved alloy is characterized chiey by its capability of being air-hardened. In its annealed condition it may be readily machined, but is capable of being hardened within wide ranges of temperature, and during the hardening process may be cooled in air, with a minimum danger of cracking,

i5 warping or shrinking. I'Ieat treatment may be carr1ed out with less than the ordinary precautions necessary with common types of alloys. 'Ihe alloy shows an unusual uniformity and depth of hardening, yet is cal pable of selective hardening to a marked deee, the hard portions, such as the wearing ace of a gear, may be file hard, while'the softer portions, such as the gear center, may

be machinable with only slight .diiculties 467,201, led May 5, 1921. 1922. Serial No. 535,689.

nickel and A This application filed February i1,

'Ihe alloy is capable of being hardened sumciently for all practical purposes by the simple process of air-hardening.-

As a result of extensive experiments with my alloy, I find that it is desirable to restrict the ranges of the elements to certain relative proportions, particularly as to the carbon, chromium and molybdenum contents,'as the air-hardening qualities apparently depend largely upon the proportions of these elements. 'Ihe nickel, in limited proportions specified, is essential to add toughness to thel metal, but in excessive quantities the alloy becomes diiiicult to anneal, and shows a tendency to crack during heat treatment.

For most uses, best results are obtained by confining the ranges of the carbon, chro-` mium and molybdenum to the following ranges:

Carbon .50to .85A Chromium Q .40 to .95 Molybdenum .30 to .80

And the nickel ranging from .50 to 2.00%, depending upon the toughness desired. IVithin the ranges above specified, the alloy exhibits the maximum air-hardening characteristics consistent with economy and uniformity in results in the production of the alloy.

In the accompanying Figures 1 and 2, I have illustrated graphically the preferable proportions of the elements within these ranges. For instance, if .65% carbon is to be used, reference to Figure 1 shows that .55-.60% chromium is recommended, and reference to Figure 2 shows that .50-.55% molybdenum is recommended. As before stated, nickel may range from about .50 to 2.00% in all cases, depending upon toughness desired. From these figures, therefore, three typical analyses may be derived, as follows:

'Ihese analyses are suggestive, of the ranges in which maximum air-hardening qualities may be obtained, but it will be understood that these proportions` may be.v

varied considerably within the ranges specified. Furthermore,'substantia1 air-hardening qualities may be obtained by varying the proportions beyond the ranges described in connection with Figures 1 and 2. vFor instance, a carbon content as low as .3G-.40% might be used. Reference to the tables shows the general rule to be cthat the chromium and molybdenum should be increased as the carbon content is decreased. Therefore, with .30-.40% carbon, approximately the following analysis is recommended for best air-hardening qualities:

Carbon .30.- .40 Chromium 1.00-1.10 Molybdenum i 1.50-2.00 Nickel 1 1 1.00-1.50

the analysis which will probably be suitablefor most purposes. This form has a consta-nt Carbon range from .50% to .60%, with the molybdenum decreasing' from about .80% to..30% while the chromium ranges in inverse proportion from about .40% to .95%.

A typical heat treatment of my alloy isas follows: The piece is annealed for machining preferably by heating it to about 1400 degree Fahrenheit and cooling in the furnace. The ncritical temperature 1s about 1350 to 1355 degrees Fahrenheit. Hardening is accomplished by heating to approximately 1600 degrees Fahrenheit and coolin the piece in still air or in a blast, or, i desired, by quenching.- The tempermay be drawn as desired by reheating in the usual manner to the desired point.

My improved alloy hasv a wide range of uses, but is particularly adapted for use in machine parts which" are irregular in shape,

or have relatively heavy and light portions," such as ordinarily are subject to warpingl or shrinking after they have been machined to size and are heat treated by ordinaryl methods. When such pieces are made of my improved steel allo they are readily machmable, in anneale condition, but are caable .of being hardened in air suiiiciently o or ordinary purposes without appreciable warping.shrinking or cracking.` vIn .case greater hardness is desired, the pieces may be quenched.` Hardening and drawing of temper may be accomplished with less than ordinary care, as the variation in physical praperties for given dilferences in temperature is smallery than in the case of ordinary alloy steels,

I claim as my invention:

k 1. A steel alloy containin carbon ranging from .50% to .85%; c romium from '40% to .95%'; lmolybdenum from .30% to .80%, and nickel from *.50% to 2.00%.

2. A steel a-lloy containin carbon ranging from .50% to .85%, nic el from .50% -to 2.00%; chromium varying from .410% to .95% and inversely as the carb-on content, and molybdenum varying from .30% to .80% inversely as the carbon content, substantially as described.

3. A steel alloy containing carbon .50% to .60%, nickel .50% to 2.00%, and chromium varying from .40% to .95% inversely as the molybdenum content varies from .30% to -.80%, substantially-as described.

4. A steel alloy containing carbon .30%.

to .50%; nickel from .50% to l2.00%; molyb- -denum varying from .80% to 2.00%, ap` proximately in inverse proportion to the carbon content, and 4chromium varying fromr .95% to 1.10%, approximately 1n inverse proportion to the carbon content.

5. A steel l` alloy containing carbon .30% o to 1.10%; nickel from .50% to 2.00%;

molybdenum` from .15%. to.-f2.00%, and

chromium from .25% to 1.10%, the m01yb v denum and Ichromium contents respectively varying in approximately inverse proportions to the carbon content. 6. A steel alloy containing carbon .30 to 1.00 per cent, nickel .50 to 2.00 r cent, chromium .25 to 1.10 per cent, an molybdenum .l5 to 2.00` er cent. i

7. As a new artic e of manufacture, a dieblock orf the like containing carbon. .30 to 1.00%, nickel in substantial fractions up to 2.00%, chromium in substantial fractions up to1.10%, and molybdenum in substantial fractions up to 2.00%, and iron approximately sulicient to complete the 8. A steel alloy containing carbon approx- "imately .50 per cent, nickel approximately WILL-'IAM F. FINKL. 

